Recently, lithium secondary batteries have received the most attention due to their characteristics of high energy density and long lifetime. In general, a lithium secondary battery includes an anode formed of a carbon material or a lithium metal alloy, a cathode formed of lithium metal oxide, and an electrolyte in which a lithium salt is dissolved in an organic solvent.
Lithium has been initially used as an anode active material constituting the anode of the lithium secondary battery. However, lithium may have low reversibility and safety, a carbon material has currently been mainly used as the anode active material of the lithium secondary battery. Although the carbon material may have a capacity smaller than that of lithium, the carbon material may have small volume changes and excellent reversibility, and may be advantageous in terms of cost.
However, the demand for high-capacity lithium secondary batteries has gradually increased as the use of the lithium secondary battery has expanded. As a result, a high-capacity electrode active material replaceable with a low-capacity carbon material has been required. For this purpose, research into using a (semi) metal, such as silicon (Si) and tin (Sn), which exhibits a charge and discharge capacity higher than that of a carbon material and is electrochemically alloyable with lithium, as an electrode active material has been undertaken.
Among the above materials, since a silicon-based material has a capacity (4190 mAh/g) 11 times or more higher than a theoretical capacity (372 mAh/g) of a carbon-based anode active material, the silicon-based material is on the spotlight as a material for replacing the carbon-based anode active material. However, since volume expansion of the silicon-based material during the intercalation of lithium ions is 3 times or more when the silicon-based material is only used, a capacity of a battery tends to decrease as charging and discharging of the battery proceed, and the silicon-based material may separate from a current collector due to the volume expansion.